Prior-art measuring devices of this type measure as the physical parameter either the volume of the urine or the urine flow. This is performed according to a rotation-dynamic, gravimetric, or capacitive method, or, especially in the case of volume measurement, on the basis of the pressure of the liquid in a collecting beaker.
A measuring device of this class has been known from West German Patent Specification No. 30,07,855. Here, the measuring head is formed by a U-shaped measuring tube arranged essentially horizontally with a slight slope, through which the patient's urine flows and which is mounted inside a housing in a freely oscillating manner, with the funnel opening into the inlet port of the measuring head and the outflow port of the measuring head being arranged outside the housing. The patient's urine flows through the U-shaped measuring tube, which contains only a portion of the total amount of urine from a complete micturition, so that the measuring tube may be very small. However, the necessity to mount the U-shaped measuring tube in a freely oscillating manner inside the housing is disadvantageous.
A Uroflow measuring device of this class must also be able to be installed in the bathroom in the urological office, so that the urine can flow off directly. This permits only the use of a device which does not collect the urine. However, much greater importance is attached to accurate volume measurement in clinical urodynamic investigations. The urine is collected in a beaker at the measuring device. Furthermore, accurate representation of the flow curve as a function of time is very important for diagnosis. This is possible only when the flow is measured directly. When double differentiation is required for volume-based measurement to represent the increase in flow, the calculated result will be too inaccurate because of the effect of disturbances e.g., vibrations and wave movements of the liquid collected. Emptying of the collected liquid is too expensive in urological practice because of the great number of uroflow tests performed as a preliminary examination.
Volume calculation in flow-measuring devices is subject to great errors due to integration over time, precisely in the minimal flow range. Volume measurement is superior to flow measurement in this respect.